diff --git a/kernel_tuner/backends/cupy.py b/kernel_tuner/backends/cupy.py
index 51613be7..6b0c19b0 100644
--- a/kernel_tuner/backends/cupy.py
+++ b/kernel_tuner/backends/cupy.py
@@ -10,8 +10,10 @@
 # and run tests without cupy installed
 try:
     import cupy as cp
+    import cupyx
 except ImportError:
     cp = None
+    cupyx = None
 
 
 class CupyFunctions(GPUBackend):
@@ -68,7 +70,7 @@ def __init__(self, device=0, iterations=7, compiler_options=None, observers=None
 
         # collect environment information
         env = dict()
-        cupy_info = str(cp._cupyx.get_runtime_info()).split("\n")[:-1]
+        cupy_info = str(cupyx.get_runtime_info()).split("\n")[:-1]
         info_dict = {
             s.split(":")[0].strip(): s.split(":")[1].strip() for s in cupy_info
         }
diff --git a/test/test_cupy_functions.py b/test/test_cupy_functions.py
index 4bb4d16f..9bd328dd 100644
--- a/test/test_cupy_functions.py
+++ b/test/test_cupy_functions.py
@@ -1,4 +1,11 @@
 
+import numpy as np
+
+try:
+    from unittest.mock import patch, Mock, MagicMock
+except ImportError:
+    from mock import patch, Mock, MagicMock
+
 import kernel_tuner
 
 from .context import skip_if_no_cupy
@@ -10,3 +17,25 @@ def test_tune_kernel(env):
     result, _ = kernel_tuner.tune_kernel(*env, lang="cupy", verbose=True)
     assert len(result) > 0
 
+
+@patch('kernel_tuner.backends.cupy.cupyx')
+@patch('kernel_tuner.backends.cupy.cp')
+def test_cupy_init_uses_cupyx_not_private_attr(cp_mock, cupyx_mock):
+    """Regression test: CupyFunctions should use cupyx.get_runtime_info(), not cp._cupyx."""
+    # Setup cp mock
+    dev_mock = MagicMock()
+    dev_mock.attributes = {"MaxThreadsPerBlock": 1024}
+    dev_mock.compute_capability = "75"
+    cp_mock.cuda.Device.return_value = dev_mock
+    cp_mock.cuda.runtime.driverGetVersion.return_value = 11000
+
+    # Setup cupyx mock to return runtime info string
+    runtime_info = "CuPy Version          : 14.0.1\nCUDA Root             : /usr/local/cuda\nDevice 0 Name         : Tesla T4\n"
+    cupyx_mock.get_runtime_info.return_value = runtime_info
+
+    from kernel_tuner.backends.cupy import CupyFunctions
+    dev = CupyFunctions(device=0)
+
+    # Verify cupyx.get_runtime_info() was called, not cp._cupyx.get_runtime_info()
+    cupyx_mock.get_runtime_info.assert_called_once()
+    assert dev.name == "Tesla T4"